Allow run_line_magic to be called from scripts

Don't blow up if looking back up the stack trace fails.

Reported on rpy2: https://bitbucket.org/lgautier/rpy2/issue/184
/valueerror-call-stack-is-not-deep-enough

IPython/core/interactiveshell.py

@@ -3102,7 +3102,15 b' class InteractiveShell(SingletonConfigurable):'
         namespace.
         """
         ns = self.user_ns.copy()
-        ns.update(sys._getframe(depth+1).f_locals)
+        try:
+            frame = sys._getframe(depth+1)
+        except ValueError:
+            # This is thrown if there aren't that many frames on the stack,
+            # e.g. if a script called run_line_magic() directly.
+            pass
+        else:
+            ns.update(frame.f_locals)
+
         try:
             # We have to use .vformat() here, because 'self' is a valid and common
             # name, and expanding **ns for .format() would make it collide with